In the manufacture of an electronic device, a plasma processing method is executed using a plasma processing apparatus to process a workpiece. The plasma processing apparatus generally includes a chamber body, a gas supply unit, a stage, a first radio frequency power supply, and a second radio frequency power supply. The gas supply unit is configured to supply a gas to the inner space of the chamber body. The stage is provided in the inner space of the chamber body and is configured to support a workpiece placed thereon. The workpiece is placed on the stage such that the center thereof is located on a central axis of the chamber body. The stage includes a lower electrode. The first radio frequency power supply is configured to generate first radio frequency waves for generating plasma. The second radio frequency power supply is configured to generate second radio frequency waves. A frequency of the second radio frequency waves is lower than a frequency of the first radio frequency waves. The second radio frequency waves are supplied to the lower electrode. In the plasma processing method using the plasma processing apparatus, the gas is excited in the inner space by the first radio frequency waves, so that plasma is generated. In addition, the second radio frequency waves are supplied to the lower electrode. Thus, ions in the plasma are accelerated toward the workpiece, and the workpiece is irradiated with the accelerated ions.
As a type of plasma processing method, there is a plasma processing method in which two plasma processings are sequentially applied to a workpiece. Such a plasma processing method is described in Japanese Patent Laid-Open Publication No. 2015-173240. The plasma processing method disclosed in Japanese Patent Laid-Open Publication No. 2015-173240 is executed to selectively etch a first region formed of silicon oxide with respect to a second region formed of silicon nitride. In the plasma processing method, a processing using plasma of a fluorocarbon gas and a processing using plasma of a rare gas are executed. In the processing using the plasma of the fluorocarbon gas, a deposit film containing fluorocarbon is formed on the workpiece. While the processing using the plasma of the fluorocarbon gas is executed, power of the second radio frequency waves is set to relatively low power (e.g., 0 watts). In the plasma processing using the rare gas, the workpiece is irradiated with ions of the rare gas. While the plasma processing using the rare gas is executed, the second region is protected by the deposit film, and the first region is etched by radicals of the fluorocarbon in the deposit film. While the plasma processing using the rare gas is executed, power of the second radio frequency waves is set to relatively high power. The plasma processing method is used to form an opening in a self-aligned manner by etching the first region provided in a recess provided by the second region.